A question of dynamics

Abstract: In response to different stimuli many transcription factors (TFs) display different activation dynamics that trigger the expression of specific sets of target genes, suggesting that promoters have a way to decode dynamics. In this talk, I will present results based on a light-responsive synthetic TF, which we built using well-characterized components and LINuS, a blue light-dependent nuclear localization signal previously developed in our lab. I will show how we used this system to directly manipulate the nuclear localization of the synthetic TF in mammalian cells, generating two different pulsatile and sustained TF dynamics. Using live cell microscopy and mathematical modelling, we analysed the behaviour of a library of reporter constructs and found that decoding of TF dynamics occurs only when the coupling between TF binding and transcription pre-initiation complex formation is inefficient. We also found that the ability of a promoter to decode TF dynamics gets amplified by inefficient translation initiation. Using the knowledge acquired, we built a synthetic circuit that allows obtaining two gene expression programs depending solely on TF dynamics. Finally, I will show how our findings with the synthetic TF can be applied to two natural TFs: p65 and p53. These results help elucidate how gene expression is regulated in mammalian cells and open up the possibility to build complex synthetic circuits steered by TF dynamics.

Host: Filippo Menolascina